[Bug fortran/47915] New: Type declaration: Recursive specification expression not detected.

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47915

           Summary: Type declaration: Recursive specification expression
                    not detected.
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid, diagnostic
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org


Based on
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/8c8effead3390ad2

The following is invalid as the LEN= specification expression is circular and
-- with the "+1" in LEN not possible.

(I think without "+1" it might work as the implicit typing has len=1, which is
then used to type "a" which can then used for "b" and which then matches the
initial value of 1. It is probably still invalid, but at least not
contradictory.)

>From the standard:

"A variable in a specification expression shall have its type and type
parameters, if any, specified by a previous declaration in the same
scoping unit, by the implicit typing rules in effect for the scoping
unit, or by host or use association. If a variable in a specification
expression is typed by the implicit typing rules, its appearance in any
subsequent type declaration statement shall confirm the implied type and
type parameters." (F2008, 7.1.11 Specification expression)

Test case - only g95 complains:

Error: Circular specification in variable 'a' at (1)

gfortran accepts it even with -std=f95

  subroutine foo(a, b)
    implicit character (A-Z)
    character(len=len(b)+1) :: a
    character(len=len(a)+1) :: b 
  end